Conventionally, absorbent sheets used for pet animals are known. For example, Patent Literature 1 discloses an absorbent sheet including a liquid-permeable topsheet, a liquid-impermeable backsheet and an absorbent core interposed between these sheets. This known absorbent sheet includes a flap in which the absorbent core does not exist and a region in which the absorbent core exists therein so that the region in which the absorbent core exists may be laid on the floor and the flap may be attached to the wall in use. Patent Literature 2 discloses an absorbent sheet including a water-absorbent structure and a lining vinyl-cover. In this known absorbent sheet, the water-absorbent structure is formed with a fold extending to bisect the sheet into two sections so that one of these two sections may be attached to the floor and the other section may be attached to the wall in use. In this way, it is possible for the section attached to the wall to prevent the wall from being soiled with urine even when a male dog voids against the wall.